title: A common mechanism underlying amyloid fibrillation and protein crystallization revealed by the effects of ultrasonication.
abstract: Protein crystals form in supersaturated solutions via a nucleation and growth mechanism. The amyloid fibrils of denatured proteins also form via a nucleation and growth mechanism. This similarity suggests that, although protein crystals and amyloid fibrils are distinct in their morphologies, both processes can be controlled in a similar manner. It has been established that ultrasonication markedly accelerates the formation of amyloid fibrils and simultaneously breaks them down into fragmented fibrils. In this study, we investigated the effects of ultrasonication on the crystallization of hen egg white lysozyme and glucose isomerase from Streptomyces rubiginosus. Protein crystallization was monitored by light scattering, tryptophan fluorescence, and light transmittance. Repeated ultrasonic irradiations caused the crystallization of lysozyme and glucose isomerase after cycles of irradiations. The size of the ultrasonication-induced crystals was small and homogeneous, and their numbers were larger than those obtained under quiescent conditions. Switching off ultrasonic irradiation when light scattering or tryptophan fluorescence began to change resulted in the formation of larger crystals due to the suppression of the further nucleation and fractures in preformed crystals. The results indicate that protein crystallization and amyloid fibrillation are explained on the basis of a common phase diagram in which ultrasonication accelerates the formation of crystals or crystal-like amyloid fibrils as well as fragmentation of preformed crystals or fibrils.
authors.affiliation: Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kitayama
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: Masatomo
authors.initials: M
authors.lastname: So
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Sakurai
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yagi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Goto
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry*; D000682:Amyloid / Q000737:chemistry*; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry*; D002645:Chickens; D003460:Crystallization; D009113:Muramidase / Q000737:chemistry*; D013302:Streptomyces / Q000201:enzymology*; D014465:Ultrasonics
chemical_list: D000682:Amyloid; D001426:Bacterial Proteins; D009113:Muramidase; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase
keywords: Crystallization; Nucleation and growth; Solubility; Supersaturation; Ultrasonication